ncli_db: more readonly support (#3411)

Update several `ncli_db` commands to run in readOnly mode, allowing them
to be used with a running instance - in particular era export.

* export all eras by default
* skip already-exported eras

beacon_chain/beacon_chain_db.nim

@@ -1082,6 +1082,7 @@ iterator getAncestorSummaries*(db: BeaconChainDB, root: Eth2Digest):
     # from the old format, this brings down the write from minutes to seconds
     stmt.dispose()
 
+    if not db.db.readOnly:
       if newSummaries.len() > 0:
         db.withManyWrites:
           for s in newSummaries:
@@ -1092,6 +1093,7 @@ iterator getAncestorSummaries*(db: BeaconChainDB, root: Eth2Digest):
       db.db.exec(
         "DELETE FROM kvstore WHERE key >= ? and key < ?",
         ([byte ord(kHashToBlockSummary)], [byte ord(kHashToBlockSummary) + 1])).expectDb()
+
   var row: stmt.Result
   for rowRes in exec(stmt, root.data, row):
     expectDb rowRes

ncli/ncli_db.nim

@@ -132,9 +132,9 @@ type
         defaultValue: 0
         desc: "The era number to write".}: uint64
       eraCount* {.
-        defaultValue: 1
+        defaultValue: 0
         name: "count"
-        desc: "Number of eras to write".}: uint64
+        desc: "Number of eras to write (0=all)".}: uint64
 
     of DbCmd.importEra:
       eraFiles* {.
@@ -314,7 +314,7 @@ proc cmdBench(conf: DbConf, cfg: RuntimeConfig) =
   printTimers(false, timers)
 
 proc cmdDumpState(conf: DbConf) =
-  let db = BeaconChainDB.new(conf.databaseDir.string)
+  let db = BeaconChainDB.new(conf.databaseDir.string, readOnly = true)
   defer: db.close()
 
   let
@@ -352,7 +352,7 @@ proc cmdPutState(conf: DbConf, cfg: RuntimeConfig) =
       db.putState(state)
 
 proc cmdDumpBlock(conf: DbConf) =
-  let db = BeaconChainDB.new(conf.databaseDir.string)
+  let db = BeaconChainDB.new(conf.databaseDir.string, readOnly = true)
   defer: db.close()
 
   for blockRoot in conf.blockRootx:
@@ -391,7 +391,7 @@ proc cmdPutBlock(conf: DbConf, cfg: RuntimeConfig) =
 
 proc cmdRewindState(conf: DbConf, cfg: RuntimeConfig) =
   echo "Opening database..."
-  let db = BeaconChainDB.new(conf.databaseDir.string)
+  let db = BeaconChainDB.new(conf.databaseDir.string, readOnly = true)
   defer: db.close()
 
   if (let v = ChainDAGRef.isInitialized(db); v.isErr()):
@@ -422,7 +422,7 @@ func atCanonicalSlot(blck: BlockRef, slot: Slot): BlockSlot =
     blck.atSlot(slot - 1).blck.atSlot(slot)
 
 proc cmdExportEra(conf: DbConf, cfg: RuntimeConfig) =
-  let db = BeaconChainDB.new(conf.databaseDir.string)
+  let db = BeaconChainDB.new(conf.databaseDir.string, readOnly = true)
   defer: db.close()
 
   if (let v = ChainDAGRef.isInitialized(db); v.isErr()):
@@ -443,7 +443,8 @@ proc cmdExportEra(conf: DbConf, cfg: RuntimeConfig) =
     tmp: seq[byte]
     timers: array[Timers, RunningStat]
 
-  for era in conf.era ..< conf.era + conf.eraCount:
+  var era = conf.era
+  while conf.eraCount == 0 or era < conf.era + conf.eraCount:
     if shouldShutDown: quit QuitSuccess
     let
       firstSlot =
@@ -457,6 +458,9 @@ proc cmdExportEra(conf: DbConf, cfg: RuntimeConfig) =
       break
 
     let name = withState(dag.headState.data): eraFileName(cfg, state.data, era)
+    if isFile(name):
+      echo "Skipping ", name, " (already exists)"
+    else:
       echo "Writing ", name
 
       let e2 = openFile(name, {OpenFlags.Write, OpenFlags.Create}).get()
@@ -476,6 +480,8 @@ proc cmdExportEra(conf: DbConf, cfg: RuntimeConfig) =
             group.finish(e2, state.data).get()
         do: raiseAssert "withUpdatedState failed"
 
+    era += 1
+
   printTimers(true, timers)
 
 proc cmdImportEra(conf: DbConf, cfg: RuntimeConfig) =
@@ -494,6 +500,8 @@ proc cmdImportEra(conf: DbConf, cfg: RuntimeConfig) =
 
   var data: seq[byte]
   for file in conf.eraFiles:
+    if shouldShutDown: quit QuitSuccess
+
     let f = openFile(file, {OpenFlags.Read}).valueOr:
       warn "Can't open ", file
       continue
@@ -550,7 +558,7 @@ type
 proc cmdValidatorPerf(conf: DbConf, cfg: RuntimeConfig) =
   echo "Opening database..."
   let
-    db = BeaconChainDB.new(conf.databaseDir.string,)
+    db = BeaconChainDB.new(conf.databaseDir.string, readOnly = true)
   defer:
     db.close()